The 2002-2017 X-ray Decline of the Narrow Line Seyfert 1 galaxy WPVS 007
ATel #13434; Sol Gutierrez-lara, Sasha Bates (Commonwealth School, Boston), Antonella Fruscione, Jeremy J. Drake (Smithsonian Astrophysical Observatory)
on 31 Jan 2020; 22:57 UT
Credential Certification: Jeremy J. Drake (jdrake@cfa.harvard.edu)
Subjects: X-ray, AGN, Black Hole
We report on the lowest observed X-ray flux state of the Narrow Line Seyfert 1 galaxy WPVS 007 (RA: 00 39 15.80, DEC: -51 17 03.00). Since its detection as a bright X-ray source with a luminosity slightly below 1043 erg s-1 (S. Vaughan, R. Edelson and R. S. Warwick, 2004) in the ROSAT All-Sky Survey of 1990, four Chandra observations of WVPS 007 over the past 20 years show a general decline in its X-ray emission. The first Chandra observation, made in August 2002, recorded a significantly lower flux of 0.89E-14 erg s-1 cm-2 (S. Vaughan, R. Edelson and R. S. Warwick, 2004, MNRAS, 349, L1) with an ACIS-S3 count rate of 1.05 +/- 0.045 count/ks. We have obtained data for all three subsequent ACIS-S3 observations from the Chandra archive and assessed count rates and model-independent fluxes within the 0.5-7 keV bandpass using the srcflux tool within ds9. After an eight-year gap, the 2010 June observation had a count rate of 2.21 +/- 0.35 count/ks and a flux of (1.02 +/- 0.28)E-14 erg s-1 cm-2, followed by a March 2015 observation with a count rate of 1.22 +/- 0.38 count/ks and a flux of (6.82+/- 3.6)E-15 erg s-1 cm-2. The most recent Chandra observation, made in March 2017, recorded a count rate of 0.55 +/- 0.29 count/ks and an X-ray flux of (4.6 +/- 3.1)E-15 erg s-1 cm-2, the lowest it has been in 30 years of observation. Correlated with this decline in X-ray emission was a sudden and dramatic decline in UV flux between the 2010 and 2015 observations (Leighly et al. 2015, ApJ, 809, L13). However, in the epoch of the last Chandra observation in March 2017, WPVS 007 was in a moderately bright UV state (Li et al., 2017 MNRAS, 487, 4592).
